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Chapter 2-01: Anatomy and Physiology in Pulmonology

ANATOMY OF THE LUNGS

FIGURE 2.1

Anatomy of the lungs. Shown are the five lobes of the lung and the anatomy of the tracheobronchial tree.

An image shows the diagrammatic representation of the anatomy of the lungs with five lobes and the tracheobronchial tree. The lungs in the left and the right has many sub branches the predominantly distributed all over the half c shaped structure. At left side it’s consist of two segments one prominent and another at bottom. At right side it consists of three segments with equal distribution that is superior, middle and inferior lobe, respectively. The tube is called as the trachea.
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OVERVIEW

  • Mechanics:

    • - Statics refer to forces acting on the lung that affect volumes and elastic behavior

      • Lungs = collapsing forces; chest wall (CW) = expanding forces (Figure 2.2)

    • - Dynamics refer to the forces moving air, including flow patterns and resistance

  • Gas exchange: Handling of O2/CO2

FIGURE 2.2

The lung–chest wall system. The chest wall has a tendency toward expansion, while the lungs have a tendency toward collapse. At the end of a normal exhalation, the volume of air remaining in the lungs is the functional reserve capacity. While at the functional reserve capacity, the expanding chest wall forces and the collapsing lung forces are in balance. Since initiating a new breath requires the lung–chest wall system to shift away from this equilibrium point, inhalation is an active process that requires the use of the respiratory muscles.

An image shows the graphical representation of the lung chest wall system based on the volume and trans organ static pressure. The vertical axis denotes the volume in liter from one to six, bottom to top and the horizontal axis denotes the trans organ static pressure from minus twenty to forty. Two horizontal dotted lines are drawn at 6 and 2.3 in the vertical axis and labeled as total lung capacity, and functional reserve capacity respectively. A vertical line is drawn at 0 in the horizontal axis. A curve labeled chest wall is drawn from (negative 20, 1) to (5, 6). Another curve labeled lung-chest wall system is drawn from (negative 18, 1) and ends at (35, 6). A curve labeled lung is drawn from (0, 0.5) to (35, 6). A small dashed line is drawn from (0, 0.5) to (negative 10, 0.5).
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STATICS: VOLUMES/CAPACITIES, COMPLIANCE, AND SURFACE TENSION

  • Volumes and Capacities:

    • - Definitions (Table 2.1)

    • - Changes in pathologic states (Figure 2.3)

      • Obstructive lung disease (e.g., asthma, emphysema): ↑TLC, FRC, RV; ↓↓FEV1, ↓FVC, FEV1/FVC < 0.7

      • Restrictive lung disease (e.g., fibrosis): ↓TLC, FRC, RV; ↓FEV1, ↓↓FVC, ↑ or normal FEV1/FVC

  • Compliance: C = ΔV/ΔP

    V = volume, P = pressure

    • - Compliance = Filling term; ability of lungs to stretch

    • - Elastance = Expiration term; ability of lungs to collapse from stretched position

    • - Obstructive diseases = ↑Compliance, ↓Elastance; Restrictive diseases = ↓Compliance, ↑Elastance

  • Surface tension: P = 2T/r

    P = pressure, T = surface tension, r = radius

    • - Law of Laplace: Large alveoli remain open due to high radius, and small alveoli collapse, causing atelectasis

    • - Surfactant:

      • Decreases surface tension → Decreases pressure → Increases compliance and reduces alveolar collapse

      • Produced by Type II alveolar cells: Choline + diacylglycerol → dipalmitoylphosphatidylcholine (DPPC)

      • Surfactant contains lecithin; if lecithin:sphingomyelin ratio ≥ 2:1 in amniotic fluid = lung maturity

    • - Hysteresis: Compliance (i.e., the slope of a pressure/volume curve) changes with inspiration and expiration; compliance is lower during expiration and at extreme volumes (i.e., very full lungs or very empty lungs)

FIGURE 2.3

Lung volumes and capacities in health and disease. A) The four components of volume in the lung: Tidal volume (TV), expiratory reserve volume (ERV), inspiratory reserve volume (IRV), and residual volume (RV), as well as capacities which are measurements of two or more volumes. Functional residual capacity (FRC) = ERV + RV. Inspiratory capacity (IC) = TV + IRV. Vital capacity (VC) = ...

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